We have a retro/vintage sewing supply.  It is a cutwork polyester wide long collar a bit heavier than a t shirt fabric and supported in the back to give it a bit more body.  It measures about 18" down the front flat side which is to be sewed onto the garment x about 4 3/4" across the top flat edge and 2" across the lower ends.  The widest the collar is in the center is about 6 3/4" across.  I believe this dates to the 1980's or so.  It is nos never applied.
I will ship internationally, please contact me with your country for a shipping quote.